The present invention relates to a simplified electric switch construction including movable conductive contact members having a high contact pressure for making electric connection between terminals, and more particularly to such a switch construction which is simple in structure, stable in ON-OFF operation, small in size, and contains an electronic circuit.
Various mechanisms have been devised for electric connection between terminals in switches. The known mechanisms have suffered from the problem of poor contact between contacts of movable conductive contact members and contacts of terminals (hereinafter referred to as "bridge portions"). FIG. 1 of the accompanying drawings shows a conventional switch in which a terminal 1a has a bridge portion 2a to which a contact member 3 is fixed. A contact of the contact member 3 is brought into contact with a bridge portion 2b of a terminal 1b by depressing one end 4 of the contact member 3. Since the contact 5 is pressed merely by a push against the bridge portion 2b through an area of contact, any dust or flux therebetween cannot be effectively removed. Any oxidized coating formed on the contact surfaces with time cannot be coped with, and it is necessary to plate the contact surfaces with precious metal which is chemically stable. According to another prior switch illustrated in FIG. 2, a contact member 7 normally urged downwardly by a spring 6 is moved to the right (as shown) to bring a contact 8b of the contact member 7 into contact with a bridge portion 10b of a terminal 9b while keeping a contact 8a of the contact member 7 in contact with a bridge portion 10a of a terminal 9a. This arrangement is better than the depression-type switch construction since the contact 8b is held in frictional contact with the bridge portion 10b. However, there is a structural limitation against imposing a sufficient contact pressure to remove any unwanted deposit sufficiently from the contact surfaces.
There is known a DIP (dual in-line package) switch construction having an electronic circuit responsive to operation of a switch drive unit for selecting desired terminals to achieve a certain electric fuction. The DIP switch construction is composed of ordinary DIP switch terminals connected to portions of an electronic circuit on a printed-circuit board and accommodated in a casing. Its fabrication requires separate preparation of a DIP switch and a printed-circuit board having an electronic circuit provided thereon and normally molded in a mass of resin. Therefore, the conventional DIP switch construction is likely to be increased in size. It would be possible to form the DIP switch and the printed-circuit board as an integral structure. However, prior individual switches used as DIP switches would have a structural limitation against miniaturization, and would suffer from less contact stability due to a small current to pass through the switch. No good contact would be obtained if the conventional switch contact members were pressed against contacts printed on the printed-circuit board. To avoid this shortcoming, the contacts on the printed-circuit board and contact members would have to be plated with gold, and would be provided with greater surfaces of contact.